Magallanes, Alvin
Singh, Amarjit
Sullivan, Ben
Singh, Amarjit
Sullivan, Ben
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The overall aim of the Kahului Caisson Breakwater project is to increase the tranquility within the Harbor to allow more operational days. HOV Environment was contracted to develop the detailed construction and installation methodology, along with construction cost estimates and project schedule for the proposed caisson breakwater project. This investigation was further enhanced by verifying the project schedule and running a process simulation. In order to develop a better understanding of previous breakwater caisson projects, a detailed literature review was undertaken. It became apparent during this review that there were very few instances where caissons have been used to create a submerged breakwater; most examples refer to emerged caisson units. The closest project to a submerged structure is the Costa Azul breakwater developed for a liquid natural gas (LNG) facility in Baja, Mexico. It was decided that best practices would be adopted where possible; where no new methods would be developed. After conducting the literature review and developing a list of known installation methods a detailed site study was conducted. The aim of this study was to understand any restrictions related to the construction of the project and assess the available resources in Hawaii to implement the project. Three key factors were highlighted during the site visit: (1) no construction activities could take place in Kahului Port or the island of Maui. (2) The resources in Hawaii are limited for this type of project. (3) The construction window is very limited with a maximum of 5 months during the summer season where wave height and period are lower. The proposed approach will be to use Dry Dock 4 in Pearl Harbor, Oahu. The main reason being this is the only facility in Honolulu with the appropriate draft for the caisson units. The caisson units will be cast in Dry Dock 4 using state-of-the-art slipform in one single pour to avoid any cold joints. When ready, the dock will be flooded, and then the caisson will be tested for even floatation and transported onto a heavy lift vessel. The heavy lift vessel will then transport the unit from Oahu to the project site outside Kahului Harbor. Once at the site, the caissons will be unloaded and towed into place above the prepared foundation layer. Once all four caisson units have been installed and final surveys are complete the final stage of the project is to transplant coral fragments onto the structure. Two approaches have been suggested with the use of traditional coral transplanting or incorporating a Biorock structure on the outside of the caisson whilst in the dry dock. Further research into the supply of the coral fragments will be required. After verification of the project schedule, two process simulations were run using EZStrobe. The first simulation modeled the project schedule exactly, initializing all construction activities simultaneously. This involved initialization of construction activities at the dry dock, where the caissons will be constructed, and the initialization of construction activities at the construction site, outside Kahului Harbor. The approach for the second simulation was run with the initialization of the dry dock activities independent of the construction activities at the installation site. This approach was considered due to the constraint of the construction window; to have the construction of the caissons at the dry dock well before the commencement of works done at the construction site and to investigate the effects this shift in the schedule would have on the overall project duration. The initial project schedule and cost estimates determined that the duration of the project will take 139.9 days to complete and cost approximately US$20.7 million, with contingencies. Simulation I verifies these initial estimates having a completion time of 139.12 days and cost US$22.1 million, with contingencies. For Simulation II, project duration was determined to be 143.8 days and US$22.3 million, with contingencies. These simulations show that the project can be feasibly completed within the mandatory construction window of 150 days and at a budget of about US$20 million. However, due to this project’s sensitivity to time, any delays to the project will push the duration of the project outside the 150-day window and cause a considerable increase in costs.
Alvin Magallanes, Amarjit Singh, and Ben Sullivan, CONSTRUCTION METHODOLOGIES, SCHEDULING, COSTING, AND PROCESS SIMULATION OF A SUBMERGED CONCRETE CAISSON BREAKWATER, University of Hawaii, College of Engineering, Research Report No. UHM/CEE/2017-02, Apr 2017.
110 pages
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